JP5747212B2 - Current sensor - Google Patents

Description

  The present invention relates to a current sensor that measures a current to be measured flowing through a current path in a non-contact manner.

  In fields such as motor drive technology in electric vehicles and hybrid cars, a relatively large current is handled, and thus a current sensor capable of measuring a large current in a non-contact manner is required for such applications. As such a current sensor, a sensor that detects a change in a magnetic field caused by a current flowing through a current path by a magnetosensitive element has been put into practical use.

  As a current sensor using a magnetosensitive element, a current sensor is known in which a plurality of magnetosensitive elements are arranged at equal intervals on a virtual circle centering on the central axis of a current path through which a current to be measured flows (for example, Patent Document 1). In this current sensor, the direction of the sensitivity axis of the plurality of magnetosensitive elements is the direction along the same circular direction of the virtual circle, and the influence of the disturbance magnetic field is canceled by adding the outputs of the magnetosensitive elements.

Japanese Patent Laid-Open No. 10-300795

  However, in a current sensor in which a plurality of magnetosensitive elements are arranged at equal intervals on a virtual circle centered on the central axis of the current path as described above, even if the outputs of the magnetosensitive elements are added, the influence of the disturbance magnetic field There is a problem in that it may not be sufficiently suppressed.

  The present invention has been made in view of such points, and in a current sensor in which a plurality of magnetosensitive elements are arranged at equal intervals on a virtual circle centered on the central axis of a current path through which a current to be measured flows. An object of the present invention is to provide a current sensor capable of reducing the influence of a disturbance magnetic field and improving the measurement accuracy of a current to be measured.

The current sensor of the present invention is arranged at equal intervals on a virtual circle centered on the central axis in a plane orthogonal to the central axis of the current path through which the current to be measured flows, and the first sensitivity axis and the first sensitivity A plurality of magnetosensitive elements each having a second sensitivity axis orthogonal to the axis, and an arithmetic circuit for calculating a current value flowing through the current path based on outputs of the plurality of magnetosensitive elements, The direction of the first sensitivity axis of the magnetosensitive element is parallel to the tangential direction of the virtual circle, the direction of the second sensitivity axis of the plurality of magnetosensitive elements is the radial direction of the virtual circle, and the plurality The magnetic sensor is arranged in a spiral shape around the central axis of the current path .

  According to this configuration, the directions of the first sensitivity axes of the plurality of magnetosensitive elements arranged at equal intervals on the virtual circle are parallel to the tangential direction of the virtual circle, and the second sensitivity of the plurality of magnetosensitive elements is the second. The direction of the sensitivity axis is the radial direction of the virtual circle. For this reason, by calculating the outputs of the magnetosensitive elements arranged at equal intervals on the virtual circle, it is possible to cancel the influence of the disturbance magnetic field appearing not only on the first sensitivity axis but also on the second sensitivity axis, The measurement accuracy of the current to be measured can be improved.

  In the current sensor, the direction of the first sensitivity axis of the plurality of magnetosensitive elements is a direction along the same circumferential direction of the virtual circle, and the direction of the second sensitivity axis of the plurality of magnetosensitive elements is: It is a direction along the same radial direction of the virtual circle, and the arithmetic circuit may calculate the current value by adding the outputs of the plurality of magnetosensitive elements. According to this configuration, the influence of the disturbance magnetic field appearing on the first sensitivity axis and the second sensitivity axis can be canceled only by summing (adding) the outputs of the respective magnetosensitive elements, so that the circuit configuration can be further simplified. it can.

  In the current sensor, sensitivities of the first sensitivity axes of the plurality of magnetosensitive elements may be equal to each other, and sensitivities of the second sensitivity axes of the plurality of magnetosensitive elements may be equal to each other. According to this configuration, since the sensitivities of the first sensitivity axis and the second sensitivity axis are equal, arithmetic processing can be performed without correcting the output of each magnetosensitive element, and the circuit configuration can be further simplified. .

  In each of the current sensors, each of the magnetosensitive elements has a first group in which the direction of the first sensitivity axis is a direction along one circulation direction of the virtual circle, or the direction of the first sensitivity axis is the virtual circle. The arithmetic circuit belongs to any one of the second groups that are in a direction opposite to the one direction, and the arithmetic circuit includes outputs of the magnetosensitive elements belonging to the first group and magnetosensitive elements belonging to the second group. The outputs may be summed separately, and the current value may be calculated by differentially processing the sum value in the first group and the sum value in the second group. According to this configuration, since only the magnetosensitive elements in the same group are connected in series, a large drive voltage is not required as in the case where all the magnetosensitive elements are connected in series, and each sensor caused by a shortage of drive voltages. It is possible to prevent the output quality of the magnetic element from deteriorating.

  In the current sensor, the magnetosensitive element may be a GMR element, and the second sensitivity axis may be a secondary sensitivity axis.

  In the current sensor, the second sensitivity axis may be an axis that affects sensitivity.

  According to the present invention, in a current sensor in which a plurality of magnetosensitive elements are arranged at equal intervals on a virtual circle centered on the central axis of a current path through which a current to be measured flows, the influence of a disturbance magnetic field is reduced, A current sensor that can improve the measurement accuracy of the current to be measured can be provided.

It is a figure which shows the current sensor which concerns on 1st Embodiment. It is a circuit diagram of the current sensor concerning a 1st embodiment. It is a figure which shows the current sensor which concerns on 2nd Embodiment. It is a circuit diagram of the current sensor which concerns on 2nd Embodiment. It is a figure which shows the current sensor which concerns on the example 1 of a change of 2nd Embodiment. It is a figure which shows the current sensor which concerns on the example 2 of a change of 2nd Embodiment. It is a figure which shows the current sensor which concerns on the modification 3 of 2nd Embodiment. It is a circuit diagram of the current sensor which concerns on the example 3 of a change of 2nd Embodiment. It is a figure which shows the 1st usage pattern of the current sensor of this invention. It is a figure which shows the 2nd usage pattern of the current sensor of this invention. It is a figure which shows the 3rd usage pattern of the current sensor of this invention. It is a figure which shows the 4th usage pattern of the current sensor of this invention.

  The present inventor sums up the outputs of each magnetosensitive element in a current sensor in which a plurality of magnetosensitive elements are arranged at equal intervals on a virtual circle centered on the central axis of the current path through which the current to be measured flows. It has also been found that the reason why the influence of the disturbance magnetic field cannot be sufficiently suppressed is that each magnetosensitive element has sensitivity in a direction orthogonal to the direction with the highest sensitivity (hereinafter referred to as the main sensitivity axis). For example, when a GMR element is used as the magnetosensitive element, the sensitivity in the direction with the highest sensitivity among the directions orthogonal to the main sensitivity axis (hereinafter referred to as the secondary sensitivity axis) is about several tens of percent of the sensitivity on the main sensitivity axis. Sometimes. Thus, when using a magnetosensitive element having a secondary sensitivity axis in a direction orthogonal to the main sensitivity axis, the disturbance magnetic field can be added even if the outputs of the magnetosensitive elements are added only by directing the main sensitivity axis in the direction of the induced magnetic field. The effects of can not be removed sufficiently. This is because the influence of the disturbance magnetic field appearing on the secondary sensitivity axis cannot be canceled only by controlling the primary sensitivity axis.

  Based on such knowledge, the present inventors have made a plurality of senses arranged at equal intervals on a virtual circle centered on the central axis in a plane orthogonal to the central axis of the current path through which the current to be measured flows. The idea was to cancel the influence of the disturbance magnetic field appearing on the sub-sensitivity axis by controlling the direction of the sub-sensitivity axis of the magnetic element. That is, the gist of the present invention is the direction of the main sensitivity axis (first sensitivity axis) of each magnetosensitive element arranged at equal intervals on a virtual circle centered on the central axis of the current path through which the current to be measured flows. Is configured to be parallel to the tangential direction of the virtual circle and the direction of the secondary sensitivity axis (second sensitivity axis) is the radial direction of the virtual circle, and the current value of the current path is calculated based on the output of each magnetosensitive element Is used to offset not only the disturbance magnetic field appearing on the main sensitivity axis but also the disturbance magnetic field appearing on the sub-sensitivity axis, thereby improving the measurement accuracy of the current value of the current path.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a diagram illustrating a current sensor according to the first embodiment. As shown in FIG. 1, the current sensor 1 includes a plurality of elements arranged at equal intervals on a virtual circle C centered on the central axis in a plane perpendicular to the central axis of the current path 11 through which the current to be measured flows. Magnetosensitive elements 12a, 12b, 12c and 12d are provided. FIG. 1 is a diagram showing the arrangement positions of the magnetosensitive elements 12a, 12b, 12c, and 12d in a plane orthogonal to the central axis of the current path 11. That is, FIG. 1 shows the arrangement positions of the magnetosensitive elements 12a, 12b, 12c, and 12d on a plane orthogonal to the central axis of the current path 11 when viewed from the front side of the drawing. All of the elements 12 a, 12 b, 12 c, and 12 d may be disposed on a plane orthogonal to the central axis of the current path 11.

  Alternatively, the current path 11 may be shifted from the plane in the extending direction. In the case where the current path 11 is displaced in the extending direction, the magnetosensitive elements 12a, 12b, 12c, and 12d are arranged on a plane perpendicular to the central axis of the current path 11 when viewed from the front side of the drawing. 1 is projected as shown in FIG. As an example of such a configuration, the virtual circle C includes a virtual semicircle on the first plane orthogonal to the central axis of the current path 11 and a virtual semicircle on the second plane parallel to the first plane. In addition, a configuration in which the plurality of magnetosensitive elements 12 are arranged on a virtual semicircle, and a configuration in which the plurality of magnetosensitive elements 12 are arranged in a spiral shape around the central axis of the current path 11 can be given.

  1, FIG. 3, FIG. 5 to FIG. 7 show the arrangement positions of the magnetosensitive elements 12 projected on or on a plane orthogonal to the central axis for the sake of simplicity. In this case, a structure in which a substrate or member on which the magnetosensitive element 12 is mounted is attached to the current path is adopted.

  The current path 11 is a conductive member having a circular cross section that extends in a predetermined direction (in FIG. 1, extends in the front-depth direction in the drawing). An induced magnetic field A is formed around the current path 11 by the current to be measured flowing through the current path 11. In FIG. 1, the direction of the current to be measured is the X direction, whereby a right-direction induced magnetic field A is formed around the current path 11. In the drawings, the current path 11 is a conductive member having a circular cross section. However, any configuration that can guide the current to be measured, such as a flat plate-shaped conductive member or a conductive member (conductive pattern) on a thin film, can be used. Such a form may be sufficient.

  As described above, the magnetic sensing elements 12a to 12d are arranged at equal intervals on the virtual circle C around the central axis of the current path 11 through which the current to be measured flows. The directions of the main sensitivity axes 121a to 121d of the magnetosensitive elements 12a to 12d are parallel to the tangential direction of the virtual circle C, and the directions of the secondary sensitivity axes 122a to 122h are the radial direction of the virtual circle C. The sub-sensitivity axes 122a to 122d are in a direction orthogonal to the main sensitivity axes 121a to 121d and the direction of the current to be measured flowing through the main sensitivity axes 121a to 121d and the current path 11 (the X direction in FIG. 1). Parallel. Here, the main sensitivity axes 121a to 121d are directions in which the sensitivity of the magnetosensitive elements 12a to 12d is the highest, respectively. The sub-sensitivity axes 122a to 122d are directions in which the sensitivity of the magnetosensitive elements 12a to 12d is the highest among the directions orthogonal to the main sensitivity axes 121a to 121d, respectively.

  As shown in FIG. 1, the directions of the main sensitivity axes 121 a to 121 d of the magnetic sensitive elements 12 a to 12 d are directions along the same circulation direction of the virtual circle C. In FIG. 1, the directions of the main sensitivity axes 121a to 121d are directions along the clockwise direction of the virtual circle C, but may be directions along the counterclockwise direction. The directions of the secondary sensitivity axes 122a to 122d are directions along the same radial direction of the virtual circle C, and are orthogonal to the direction of the current to be measured (X direction) flowing through the main sensitivity axes 121a to 121d and the current path 11. It is a direction parallel to the direction to do. In FIG. 1, the directions of the secondary sensitivity axes 122 to 122 d are outward in the radial direction of the virtual circle C, but may be inward in the radial direction.

  In FIG. 1, an induced magnetic field A is generated when a current to be measured flows in the current path 11. In FIG. 1, it is assumed that a disturbance magnetic field α such as geomagnetism is generated from the upper side to the lower side of the drawing. In this case, since the main sensitivity axes 121a to 121d of the magnetic sensitive elements 12a to 12d are substantially parallel to the direction of the induced magnetic field A, the induced magnetic field A is detected in each of the magnetic sensitive elements 12a to 12d. Further, since the main sensitivity axes 121b and 121d of the magnetic sensing elements 12b and 12d are substantially parallel to the direction of the disturbance magnetic field α, the disturbance magnetic field α is detected in the magnetic sensing elements 12b and 12d. However, since the main sensitivity axes 121b and 121d of the magnetic sensitive elements 12b and 12d are in the opposite directions, the disturbance magnetic field α detected by the magnetic sensitive elements 12b and 12d is canceled by the arithmetic processing described later. Further, since the sub-sensitivity axes 122a and 122c of the magnetic sensing elements 12a and 12c are substantially parallel to the direction of the disturbance magnetic field α, the disturbance magnetic field α is also detected in the magnetic sensing elements 12a and 12c. However, since the sub-sensitivity axes 122a and 122c of the magnetic sensitive elements 12a and 12c are in opposite directions, the disturbance magnetic field α detected by the magnetic sensitive elements 12a and 12c is canceled by an arithmetic process described later.

  As described above, in the current sensor 1 shown in FIG. 1, the disturbance magnetic field α detected by the main sensitivity axes 121b and 121d of the magnetic sensing elements 12b and 12d is canceled by the arithmetic processing described later. Further, the disturbance magnetic field α detected by the sub-sensitivity axes 122a and 122c of the magnetic sensitive elements 12a and 12c is also canceled by the arithmetic processing described later. That is, in the current sensor 1 shown in FIG. 1, not only the influence of the disturbance magnetic field appearing on the main sensitivity axes 121 b and 121 d but also the influence of the disturbance magnetic field appearing on the auxiliary sensitivity axes 122 a and 122 c can be eliminated. The measurement accuracy of the current to be measured can be improved.

  The magnetic sensitive elements 12a to 12d are not particularly limited as long as they have a second sensitivity axis that affects the sensitivity in addition to the first sensitivity axis, which can detect magnetism and has the highest sensitivity. For example, as the magnetosensitive elements 12a to 12d, magnetoresistive elements such as GMR (Giant Magneto Resistance) elements and TMR (Tunnel Magneto Resistance) elements, Hall elements (having a magnetic convergence plate), and the like are used. Here, when a GMR element is used, the first sensitivity axis with the highest sensitivity is called the main sensitivity axis, and the second sensitivity axis orthogonal to the first sensitivity axis is called the sub-sensitivity axis. In FIG. 1, the four magnetosensitive elements 12 a to 12 d are arranged at equal intervals on the virtual circle C, but the number of the magnetosensitive elements 12 is not limited to this, and may be an even number. This is because if the number of the magnetosensitive elements 12 is an even number, the influence of the disturbance magnetic field α can be eliminated by arranging the virtual circles C on the virtual circle C at equal intervals and performing the arithmetic processing described later.

  FIG. 2 is a circuit diagram of the current sensor according to the first embodiment. As shown in FIG. 2, the current sensor 1 includes an arithmetic circuit 13 that calculates and outputs the current value of the current path 11 based on the outputs of the magnetosensitive elements 12 a to 12 d. Specifically, the magnetosensitive elements 12a to 12d detect magnetic fields appearing on the main sensitivity axes 121a to 121d and magnetic fields appearing on the sub sensitivity axes 122a to 122d, and voltage signals Va to Vd having magnitudes proportional to the detected magnetic fields. Is output to the arithmetic circuit 13. The arithmetic circuit 13 performs addition processing on the voltage signals Va to Vd output from the magnetic sensitive elements 12a to 12d. Note that the function of the arithmetic circuit 13 may be realized by hardware or software.

For example, in the case shown in FIG. 1, the magnetosensitive element 12a detects an induced magnetic field A that is substantially parallel to the main sensitivity axis 121a and a disturbance magnetic field α that is substantially parallel to the sub-sensitivity axis 122a, and is expressed by the equation (1). The voltage signal Va is output. The magnetosensitive element 12b detects an induced magnetic field A and a disturbance magnetic field α that are substantially parallel to the main sensitivity axis 121b, and outputs a voltage signal Vb expressed by the equation (2). The magnetosensitive element 12c detects the induced magnetic field A that is substantially parallel to the main sensitivity axis 121c and the disturbance magnetic field α that is substantially parallel to the sub-sensitivity axis 122c, and outputs a voltage signal Vc represented by Expression (3). The magnetosensitive element 12d detects an induced magnetic field A and a disturbance magnetic field α that are substantially parallel to the main sensitivity axis 121d, and outputs a voltage signal Vd expressed by the equation (4). In equations (1) to (4), k is a proportional constant, and the magnetic field in the same direction as the main sensitivity axes 121a to 121d or the sub sensitivity axes 122a to 121d is +, and the magnetic field in the opposite direction is-.
Va = k * (+ A−α) (1)
Vb = k * (+ A + α) (2)
Vc = k * (+ A + α) (3)
Vd = k * (+ A−α) (4)

In the case shown in FIG. 1, the arithmetic circuit 13 adds the voltage signals Va to Vd output from the magnetosensitive elements 12 a to 12 d and calculates the current value of the current path 11 as shown in Expression (5). .
Va + Vb + Vc + Vd
= K * (+ A−α) + k * (+ A + α) + k * (+ A + α) + k * (+ A−α)
= 4 * k * A (5)
As shown in Expression (5), the disturbance magnetic field α is canceled by adding the voltage signals Va to Vb. As described above, in the current sensor 1, not only the disturbance magnetic field α appearing on the main sensitivity axes 121a to 121d but also the influence of the disturbance magnetic field α appearing on the auxiliary sensitivity axes 122a to 122d can be eliminated. For this reason, the measurement accuracy of the current value of the current path 11 can be improved.

(Second Embodiment)
Next, a current sensor according to a second embodiment will be described. In the current sensor 1 according to the first embodiment, the disturbance magnetic field appearing on the main sensitivity axis 121 and the secondary sensitivity axis 122 by summing the outputs of the plurality of magnetosensitive elements 12 arranged at equal intervals on the virtual circle C. Eliminate the effects of α. On the other hand, in the current sensor 1 according to the first embodiment, since the plurality of magnetosensitive elements 12 are connected in series, as the number of the magnetosensitive elements 12 arranged on the virtual circle C increases, More drive voltage will be required. However, since the drive voltage that can be supplied to the plurality of magnetosensitive elements 12 at a time is limited, the output quality of each magnetosensitive element 12 (for example, S / N (Signal to Noise Ratio) is reduced due to insufficient drive voltage. )) Is reduced. Therefore, in the current sensor 2 according to the second embodiment, the plurality of magnetosensitive elements 12 are divided into a plurality of groups in which the direction of the main sensitivity axis 121 is a direction along the reverse rotation direction of the virtual circle C, and By supplying the drive voltage to the output voltage, the output quality of each magnetosensitive element 12 is prevented from deteriorating due to insufficient drive voltage.

  FIG. 3 is a diagram showing a current sensor according to the second embodiment of the present invention. As shown in FIG. 3, the current sensor 2 includes a plurality of magnetosensitive elements 12 a to 12 h arranged at equal intervals on a virtual circle C around the central axis of the current path 11 through which the current to be measured flows. ing. In FIG. 3, the eight magnetosensitive elements 12 a to 12 h are arranged at equal intervals on the virtual circle C, but the number of the magnetosensitive elements 12 is not limited to this and may be an even number.

  In FIG. 3, the arrangement positions of the magnetosensitive elements 12a to 12h on the plane orthogonal to the central axis of the current path 11 when viewed from the front side of the drawing are shown. Each of the magnetic sensitive elements 12 a to 12 h may be arranged on a plane orthogonal to the central axis of the current path 11. Alternatively, the current path 11 may be shifted from the plane in the extending direction. In the case where the current path 11 is displaced in the extending direction, the positions of the magnetosensitive elements 12a to 12h are arranged on a plane perpendicular to the central axis of the current path 11 when viewed from the front side of the drawing. The projected image is as shown in FIG. As an example of such a configuration, the virtual circle C includes a virtual semicircle on the first plane orthogonal to the central axis of the current path 11 and a virtual semicircle on the second plane parallel to the first plane. In addition, a configuration in which the plurality of magnetosensitive elements 12 are arranged on a virtual semicircle, and a configuration in which the plurality of magnetosensitive elements 12 are arranged in a spiral shape around the central axis of the current path 11 can be given.

  The magnetic sensitive elements 12a to 12h have main sensitivity axes 121a to 121h parallel to the tangential direction of the virtual circle C, and directions of currents to be measured flowing through the main sensitivity axes 121a to 121h and the current path 11 (FIG. 3). Then, there are auxiliary sensitivity axes 122a to 122h that are parallel to the direction orthogonal to the X direction. In this respect, the current sensor 1 shown in FIG. 1 and the current sensor 2 shown in FIG. 3 are common. The difference between the current sensor 1 shown in FIG. 1 and the current sensor 2 shown in FIG. 3 is in the direction of the main sensitivity axis 121 of the plurality of magnetosensitive elements 12 arranged on the virtual circle C. That is, in the current sensor 1 shown in FIG. 1, the directions of all the main sensitivity axes 121 are directions along the same rotation direction of the virtual circle C, whereas in the current sensor 2 shown in FIG. For each group, the direction of the main sensitivity axis 121 is a direction along the rotation directions of the virtual circle C opposite to each other.

  Specifically, in the current sensor 2 shown in FIG. 3, the magnetosensitive elements 12 a to 12 h are configured such that the direction of the main sensitivity axis 121 is the group B <b> 1 along one rotation direction of the virtual circle C or the main sensitivity axis 121. The direction belongs to one of the groups B2 whose direction is the direction of rotation opposite to the one direction of the virtual circle C. In FIG. 3, the magnetic sensing elements 12a to 12d that continue in the circumferential direction of the virtual circle C belong to the group B1, and the magnetic sensing elements 12e to 12h belong to the group B2. In FIG. 3, the directions of the main sensitivity axes 121a to 121d of the magnetosensitive elements 12a to 12d belonging to the group B1 are directions along the clockwise direction of the virtual circle C. On the other hand, the direction of the main sensitivity axes 121e to 121h of the magnetic sensitive elements 12e to 12h belonging to the group B2 is a direction along the counterclockwise direction opposite to that of the group B1. As described above, in the current sensor 2 shown in FIG. 3, the directions of the main sensitivity axes 121a to 121h are the directions along the opposite rotation directions of the virtual circle C for each group. Note that the directions of the auxiliary sensitivity axes 122a to 122h are directions along the same radial direction of the virtual circle C (radially outward in FIG. 3) regardless of the group.

  FIG. 4 is a circuit diagram of a current sensor according to the second embodiment. As shown in FIG. 4, the current sensor 2 includes an arithmetic circuit 13 that calculates and outputs the current value of the current path 11 based on the outputs of the magnetosensitive elements 12 a to 12 h. The arithmetic circuit 13 sums up the voltage signals Va to Vd output from the magnetic sensing elements 12a to 12d belonging to the group B1, and the voltage signal Va to output from the magnetic sensing elements 12e to 12h belonging to the group B2. An adder circuit 131b for summing Vd and a differential amplifier 132 for differentially processing the sum of the voltage signals Va to Vd in the adder circuit 131a and the sum of the voltage signals Ve to Vh in the adder circuit 131b. Note that the function of the arithmetic circuit 13 may be realized by hardware or software.

Here, as described with reference to FIG. 3, the direction of the main sensitivity axes 121a to 121d of the magnetic sensitive elements 12a to 12d belonging to the group B1, and the main sensitivity axis 121e of the magnetic sensitive elements 12e to 12h belonging to the group B2. The direction of ˜121h is a direction along the rotation directions opposite to each other of the virtual circle C. More specifically, in FIG. 3, the main sensitivity axes 121a to 121d of the magnetosensitive elements 12a to 12d are in the same direction as the direction of the induced magnetic field A, respectively. For this reason, the total value of the voltage signals Va to Vd in the adder circuit 131a is expressed by Expression (6) when the description of the external magnetic field α is omitted. On the other hand, in FIG. 3, main sensitivity axes 121e to 121h of the magnetic sensitive elements 12e to 12h are opposite to the direction of the induction magnetic field A, respectively. For this reason, the total value of the voltage signals Ve to Vh in the adder circuit 131b is expressed by Expression (7) when the description of the external magnetic field α is omitted. Further, the output value from the differential amplifier 132 is expressed by Expression (8). In equations (6) to (8), k is a proportionality constant.
Va + Vb + Vc + Vd = k * (+ A) + k * (+ A) + k * (+ A) + k * (+ A)
= 4 * k * A (6)
Ve + Vf + Vg + Vh = k * (− A) + k * (− A) + k * (− A) + k * (− A)
= -4 * k * A (7)
(Va + Vb + Vc + Vd)-(Ve + Vf + Vg + Vh)
= (4 * k * A)-(-4 * k * A)
= 8 * k * A (8)

  As described above, the total value in the adder circuit 131a and the total value in the adder circuit 131b are the directions in which the main sensitivity axes 121a to 121d and the main sensitivity axes 121e to 121h are opposite to each other in the circular direction of the virtual circle C. Due to being along, the sign is reversed. Therefore, in the differential amplifier 132, by performing differential processing of the total value in the adder circuit 131a and the total value in the adder circuit 131b, an output similar to that when the magnetosensitive elements 12a to 12h are connected in series (described above) In the example, 8 * k * A) can be obtained.

  Although the description of the external magnetic field α is omitted in the above example, the external magnetic field α detected by the main sensitivity axes 121a to 121h and the sub sensitivity axes 122a to 122h of the magnetic sensitive elements 12a to 12h is the addition circuit 131a. , 131b and the differential processing in the differential amplifier 132 cancel each other out. For this reason, the output signal from the differential amplifier 132 does not include the influence of the external magnetic field α, and becomes a voltage signal proportional to the magnitude of the induced magnetic field A. The arithmetic circuit 13 calculates and outputs the current value of the current path 11 based on the output signal from the differential amplifier 132.

  As described above, in the current sensor 2 according to the second embodiment, each of the magnetosensitive elements 12 has the main sensitivity and the group B1 in which the direction of the main sensitivity axis 121 is the direction along one circumferential direction of the virtual circle C. The direction of the axis 121 belongs to any one of the groups B2 in which the direction of the virtual circle C is a direction along the rotation direction opposite to the one rotation direction. Thereby, since only the magnetosensitive elements 12 belonging to the same group are connected in series, the number of the magnetosensitive elements 12 connected in series can be reduced as compared with the case where all the magnetosensitive elements 12 are connected in series. It can prevent that the output quality of each magnetosensitive element 12 falls by lack of drive voltage. In the current sensor 2, the direction of the main sensitivity axis 121 of the magnetosensitive element 12 is a direction along the opposite rotation directions of the virtual circle C for each group, so that the outputs of the magnetosensitive elements 12 belonging to the same group are totaled. Then, by performing differential processing on the total value in each group, the same output as when all the magnetosensitive elements 12 are connected in series can be obtained. As described above, in the current sensor 2, when the number of the magnetic sensing elements 12 arranged at equal intervals on the virtual circle C increases, each of the magnetic sensing elements 12 is caused by an insufficient driving voltage of the plurality of magnetic sensing elements 12. It is possible to prevent the output quality from the output from being deteriorated and the measurement accuracy of the current path 11 from being lowered.

  Next, modifications 1 to 3 of the current sensor 2 according to the second embodiment as described above will be described. FIG. 5 is a diagram of a current sensor according to Modification 1 of the second embodiment. In FIG. 5, the arrangement positions of the magnetosensitive elements 12a to 12h in a plane orthogonal to the central axis of the current path 11 are shown. In the current sensor 2 shown in FIG. 3, the same number (four) of magnetosensitive elements 12 belong to the groups B <b> 1 and B <b> 2. However, as shown in FIG. 5, the number of magnetosensitive elements 12 belonging to each group may not be the same, and the number of magnetosensitive elements 12 belonging to one group is greater than the number of magnetosensitive elements 12 belonging to the other group. It may be less.

  For example, in the current sensor 2a shown in FIG. 5, the group B1 in which the direction of the main sensitivity axis 121 is the direction along the clockwise direction of the virtual circle C includes three magnetosensitive elements 12b, 12c, and 12d. On the other hand, the group B2 in which the direction of the main sensitivity axis 121 is a direction along the rotation direction (that is, the left rotation direction) opposite to the group B1 of the virtual circle C is composed of five magnetosensitive elements 12a and 12e to 12h. Is done. In the current sensor 2a shown in FIG. 5, the number of the magnetosensitive elements 12 directly connected in the groups B1 and B2 (that is, three in the group B1 and five in the group B2) is eight magnetosensitive elements 12a. It is reduced compared with the case of connecting ~ 12h in series. For this reason, it can prevent that the output quality from each magnetosensitive element 12 falls by lack of drive voltage, and the measurement accuracy of the current path 11 falls.

  FIG. 6 is a diagram of a current sensor according to Modification 2 of the second embodiment. In FIG. 6, arrangement positions of the magnetic sensitive elements 12 a to 12 h on a plane orthogonal to the central axis of the current path 11 are shown. In the current sensor 2 shown in FIG. 3, a plurality of magnetosensitive elements 12 arranged continuously in a direction along the same circumferential direction of the virtual circle C belong to the groups B <b> 1 and B <b> 2. However, the magnetosensitive elements 12 belonging to each group may not be continuously arranged in the direction along the same circumferential direction of the virtual circle C, and as shown in FIG. 6, the magnetosensitive elements 12 arranged adjacent to each other. May belong to different groups.

  For example, in the current sensor 2b shown in FIG. 6, the magnetosensitive elements 12a, 12c, 12e, and 12g belong to the group B1, and the magnetosensitive elements 12b, 12d, 12f, and 12h belong to the group B2. In the current sensor 2b shown in FIG. 6, when the outputs of the magnetic sensing elements 12a, 12c, 12e, and 12g of the group B1 are summed, the external magnetic field α detected by the magnetic sensing elements 12a, 12c, 12e, and 12g is canceled out. The This is because the main sensitivity axis 121a and the secondary sensitivity axis 122a of the magnetosensitive element 12a are opposite to the primary sensitivity axis 121e and the secondary sensitivity axis 122e of the magnetosensitive element 12e, respectively, and the primary sensitivity axis of the magnetosensitive element 12c. This is because 121c and the secondary sensitivity axis 122c are opposite to the primary sensitivity axis 121g and the secondary sensitivity axis 122g of the magnetic sensitive element 12g, respectively. Similarly, when the outputs of the magnetic sensitive elements 12b, 12d, 12f, and 12h of the group B2 are summed, the external magnetic field α detected by the magnetic sensitive elements 12b, 12d, 12f, and 12g is also canceled. As described above, in the current sensor 2b shown in FIG. 6, the influence of the external magnetic field α can be canceled when the outputs of the magnetosensitive elements 12 of each group are summed, so that the differential processing of the outputs of each group becomes easy.

  FIG. 7 is a diagram of a current sensor according to Modification 3 of the second embodiment. In FIG. 7, the arrangement positions of the magnetic sensitive elements 12 a to 12 h in a plane orthogonal to the central axis of the current path 11 are shown. FIG. 8 is a circuit diagram of a current sensor according to Modification 3 of the second embodiment. In the current sensor 2 shown in FIG. 3, the group B1 in which the direction of the main sensitivity axis 121 is a direction along the clockwise direction of the virtual circle C and the counterclockwise rotation of the virtual circle C in which the direction of the main sensitivity axis 121 is opposite to the group B1. Group B2, which is a direction along the direction, is provided. That is, in the current sensor 2 illustrated in FIG. 3, there are one group B1 and one group B2 in which the direction of the main sensitivity axis 121 is a direction along the same rotation direction of the virtual circle C. However, as shown in FIG. 7, a plurality of groups in which the direction of the main sensitivity axis 121 is a direction along the same rotation direction of the virtual circle C may be provided.

  For example, in the current sensor 2c shown in FIG. 7, two groups B11 and B12 in which the direction of the main sensitivity axis 121 is a direction along one rotation direction (here, the right rotation direction) of the virtual circle C, and the main sensitivity axis Two groups B21 and B22 are provided in which the direction 121 is a direction along the rotation direction (here, the left rotation direction) opposite to the groups B11 and B12 of the virtual circle C. As shown in FIG. 8, the arithmetic circuit 13 of the current sensor 2c shown in FIG. 7 includes an adder circuit 131a that sums the voltage signals Va and Vb output from the magnetosensitive elements 12a and 12b belonging to the group B11, and a group B21. An adder circuit 131b for summing up the voltage signals Vh and Vg output from the magnetic sensitive elements 12h and 12g belonging to it, and an adder circuit 131c for summing up the voltage signals Ve and Vf output from the magnetic sensitive elements 12e and 12f belonging to the group B22. And an adder circuit 131d for summing the voltage signals Vc and Vd output from the magnetosensitive elements 12c and 12d belonging to the group B12. The arithmetic circuit 13 includes a differential amplifier 133a that differentially processes the outputs of the adder circuits 131a and 131b, a differential amplifier 133b that differentially processes the outputs of the adder circuits 131c and 131d, and differential amplifiers 133a and 133b. A differential amplifier 132 for differentially processing the output is provided.

  In the current sensor 2c shown in FIG. 7, the total value in the adding circuit 131a and the total value in the adding circuit 131b are the directions of the main sensitivity axes 121a and 121b of the magnetic sensitive elements 12a and 12b and the main sensitivity of the magnetic sensitive elements 12g and 12h. Due to the fact that the directions of the shafts 121g and 121h are the directions along the reciprocal rotation directions of the virtual circle C, the positive and negative are reversed. Therefore, in the differential amplifier 133a, by performing differential processing of the total value in the adder circuits 131a and 131b, an output similar to that when the magnetosensitive elements 12a, 12b, 12h, and 12g are connected in series (for example, 4 * k * A (k is a proportional constant, A is an induced magnetic field)).

  The total value in the adder circuit 131c and the total value in the adder circuit 131d are the directions of the main sensitivity axes 121e and 121f of the magnetosensitive elements 12e and 12f and the main sensitivity axes 121c and 121d of the magnetosensitive elements 12c and 12d. Due to the fact that the imaginary circle C is in a direction along mutually opposite circulation directions, the positive and negative are reversed. Therefore, the differential amplifier 133b performs the differential processing of the total value in the adder circuits 131c and 131d, thereby outputting the same output as when the magnetosensitive elements 12e, 12f, 12c, and 12d are connected in series (for example, −4 * K * A (k is a proportional constant, A is an induced magnetic field of the current path 11)).

  Further, a combination of groups in which the total value is input to the differential amplifier 133a (here, groups B11 and B21) and a total to the differential amplifier 133b so that the outputs of the differential amplifiers 133a and 133b are reversed. A combination of groups to which values are input (here, groups B22 and B12) is determined. For this reason, the differential amplifier 132 performs differential processing on the outputs of the differential amplifiers 133a and 133b, thereby providing the same output ((4 * k * A) as when the magnetosensitive elements 12a to 12h are connected in series. − (− 4 * k * A) = 8 * k * A) can be obtained.

  In the current sensor 2 c shown in FIGS. 7 and 8, each magnetosensitive element 12 includes groups B <b> 11 and B <b> 12 in which the direction of the main sensitivity axis 121 is along the direction of one of the virtual circles C, and the direction of the main sensitivity axis 121. Belongs to one of the groups B21 and B22, which is a direction along the direction of rotation opposite to the groups B11 and B12. Since the magnetosensitive elements 12 are connected in series when belonging to the same group, the number of magnetosensitive elements 12 connected in series can be further reduced by increasing the number of groups. As described above, in the current sensor 2c shown in FIGS. 7 and 8, two groups B11 and B12 in which the direction of the main sensitivity axis 121 is a direction along one circulation direction of the virtual circle C, and the direction of the main sensitivity axis 121 is a group. By providing the groups B21 and B22, which are in a direction along the rotation direction opposite to B11 and B12, the output quality of each magnetic sensing element 12 is reduced due to a lack of drive voltage compared to the case where only the groups B1 and B2 are provided. It is possible to prevent the deterioration more effectively.

  Note that the current sensors according to the first to third modifications described above may be combined as appropriate.

(Usage of current sensor)
Next, a usage pattern of the above-described current sensor will be described. The following usage forms are the current sensor 1 according to the first embodiment, the current sensor 2 according to the second embodiment, and the current sensors 2a to 2 according to the first to third modifications of the second embodiment. It is applicable to any of 2c. Moreover, it is applicable also to the current sensor which combined suitably the modifications 1-3 of 2nd Embodiment.

  FIG. 9 is a diagram illustrating a first usage pattern of the current sensor. As shown in FIG. 9, in the first usage pattern, the above-described current sensor is mounted on one main surface 31 of the flat substrate 3. In addition, a circular opening 32 is formed at one end of the substrate 3, and a mounting portion 33 for attaching the substrate 3 to a housing (not shown) is provided at the other end of the substrate 3.

  In the opening 32, a current path 11 (not shown) through which the current to be measured flows is arranged. Specifically, the current path 11 is arranged so that the central axis of the current path 11 passes through the center of the opening 32. The current path 11 is arranged so that the central axis of the current path 11 is orthogonal to the main surface 31.

  On the main surface 31, a plurality of magnetosensitive elements 12 a to 12 h are arranged at equal intervals so as to surround the circular opening 32. As described above, the current path 11 is arranged so that the central axis of the current path 11 passes through the center of the opening 32. For this reason, the plurality of magnetosensitive elements 12 a to 12 h are arranged at equal intervals on a virtual circle C centering on the central axis of the current path 11 on the main surface 31.

  Thus, in the first usage pattern, the plurality of magnetic sensitive elements 12 a to 12 h are arranged on the main surface 31 that is the same plane that is substantially orthogonal to the central axis of the current path 11. That is, the plurality of magnetic sensitive elements 12 a to 12 h are arranged at equal intervals on a virtual circle C formed on the main surface 31 with the central axis of the current path 11 as the center. Further, as described above, the directions of the main sensitivity axes 121a to 121h of the magnetosensitive elements 12a to 12h are parallel to the tangential direction of the virtual circle C on the main surface 31, and the directions of the sub sensitivity axes 122a to 122h are This is the radial direction of the virtual circle C on the main surface 31. For this reason, in the first usage pattern, by calculating the outputs of the magnetic sensitive elements 12a to 12h, the disturbance magnetic field appearing not only on the main sensitivity axis 121 but also on the secondary sensitivity axis 122 can be canceled, and the current path 11 The measurement accuracy of the current value can be improved.

  FIG. 10 is a diagram illustrating a second usage pattern of the current sensor. FIG. 10A shows a mounting example of the above-described current sensor, and FIG. 10B shows the arrangement of the magnetic sensitive elements in the mounting example. As illustrated in FIG. 10A, in the second usage pattern, the above-described current sensor is mounted on the flexible substrate 4. The flexible substrate 4 can be formed into a substantially octagonal prism shape by bending. On the eight outer faces of the substantially octagonal prism shape formed by bending the flexible substrate 4, the magnetic sensing elements 12 a to 12 h are arranged on the same plane with the magnetic sensing faces outward. The number of surfaces formed by bending the flexible substrate 4 corresponds to the number of magnetosensitive elements 12. In FIG. 10A, since eight magnetosensitive elements 12 a to 12 h are arranged on the flexible substrate 4, the flexible substrate 4 is bent on eight sides, but is not limited thereto.

  The flexible substrate 4 is a commonly used flexible printed wiring board (FPC), and is a metal foil such as copper (Cu) provided on a film substrate made of a material such as polyimide resin (PI). However, it is patterned so as to obtain a desired wiring pattern.

  Further, as shown in FIG. 10A, the current path 11 is disposed inside a substantially octagonal prism formed by bending the flexible substrate 4. For this reason, the virtual circle C centering on the central axis of the current path 11 is formed on the same plane as shown in FIG. 10B. The plurality of magnetic sensitive elements 12a to 12h are arranged at equal intervals on a virtual circle C formed on the same plane.

  Thus, according to the second usage pattern, the plurality of magnetosensitive elements 12 a to 12 h are arranged on the same plane substantially orthogonal to the central axis of the current path 11. That is, the plurality of magnetosensitive elements 12a to 12h are arranged at equal intervals on a virtual circle C formed around the central axis of the current path 11 on the same plane. Further, as described above, the directions of the main sensitivity axes 121a to 121h of the magnetosensitive elements 12a to 12h are parallel to the tangential direction of the virtual circle C on the main surface 31, and the directions of the sub sensitivity axes 122a to 122h are This is the radial direction of the virtual circle C on the main surface 31. For this reason, in the second usage pattern, by calculating the outputs of the magnetic sensitive elements 12a to 12h, the disturbance magnetic field appearing not only on the main sensitivity axis 121 but also on the secondary sensitivity axis 122 can be canceled, and the current path 11 The measurement accuracy of the current value can be improved.

  FIG. 11 is a diagram illustrating a third usage pattern of the current sensor. FIG. 11A shows a mounting example of the above-described current sensor, and FIG. 11B shows the arrangement of the magnetosensitive elements in the mounting example. In the second usage pattern, the above-described current sensor is mounted on the flexible substrate 5. The flexible substrate 5 includes a first substrate 51, a second substrate 52 extending forward from the right side of the upper end of the first substrate 51, and extending forward from the left side of the lower end of the first substrate 51. And a third substrate 53.

  As shown in FIG. 11A, the first substrate 51 is formed to be bent forward at a predetermined angle at an intermediate position in the short side direction. The magnetosensitive element 12a is mounted on the right plane portion of the first substrate 51 bent at the predetermined angle, and the magnetosensitive element 12h is mounted on the left plane portion. Further, the second substrate 52 is formed by being bent multiple times clockwise at the same angle as the bending angle of the first substrate 51. Magnetic sensing elements 12b, 12c, and 12d are mounted on the three plane portions of the second substrate 52 bent at the predetermined angle, respectively. Further, the third substrate 53 is formed by bending a plurality of times counterclockwise at the same angle as the bending angle of the first substrate 51. Magnetic sensing elements 12e, 12f, and 12g are mounted on the three plane portions of the third substrate 53 bent at the predetermined angle, respectively.

  The flexible substrate 5 configured as described above is bent a plurality of times toward the side where the second and third substrates 52 and 53 extending from both side portions of the first substrate 51 face each other, and is seen in a plan view. It is formed to have an octagonal shape. The magnetosensitive element 12 is mounted on each planar portion of each substrate 51, 52, 53. That is, the plurality of magnetosensitive elements 12 are arranged in an annular shape in plan view. The number of planes formed by bending the flexible substrate 5 corresponds to the number of magnetosensitive elements 12. In FIG. 11A, since eight magnetosensitive elements 12 a to 12 h are arranged on the flexible substrate 5, the flexible substrate 5 has eight planes, but is not limited thereto.

  Moreover, as shown to FIG. 11A, the electric current path 11 is arrange | positioned inside each plane formed by bending the flexible substrate 5. FIG. In this case, as shown in FIG. 11B, the virtual circle C centered on the central axis of the current path 11 is parallel to the virtual semicircle Ca on the first plane orthogonal to the central axis of the current path 11 and the first plane. And a virtual semicircle Cb on the second plane. The magnetic sensing elements 12a to 12d are arranged at equal intervals on the virtual semicircle Ca on the first plane, and the magnetic sensing elements 12e to 12h are on the virtual semicircle Cb on the second plane parallel to the first plane. Arranged at equal intervals.

  According to the third usage pattern, the virtual circle C is composed of a virtual semicircle Ca on the first plane and a virtual semicircle Cb on a second plane parallel to the first plane, and a plurality of magnetosensitive elements 12a to 12h. Are arranged at equal intervals on the virtual semicircles Ca and Cb. Thereby, the magnetosensitive elements 12a to 12h are arranged at equal intervals on the virtual circle C centering on the central axis of the current path 11 in plan view. Further, as described above, the directions of the main sensitivity axes 121a to 121h of the magnetosensitive elements 12a to 12h are parallel to the tangential direction of the virtual circle C on the main surface 31, and the directions of the sub sensitivity axes 122a to 122h are This is the radial direction of the virtual circle C on the main surface 31. For this reason, in the third usage pattern, by calculating the outputs of the magnetic sensitive elements 12a to 12h, the disturbance magnetic field appearing not only on the main sensitivity axis 121 but also on the secondary sensitivity axis 122 can be canceled, and the current path 11 The measurement accuracy of the current value can be improved.

  FIG. 12 is a diagram illustrating a fourth usage pattern of the current sensor. FIG. 12A shows a mounting example of the above-described current sensor, and FIG. 12B shows the arrangement of the magnetic sensitive elements in the mounting example. In the fourth usage pattern, the above-described current sensor is mounted on the flexible substrate 6 having a substantially spiral shape. The flexible substrate 6 is formed over an angle of at least 360 ° in plan view. Further, the flexible substrate 6 is formed with planes corresponding to the number of magnetosensitive elements 12 arranged on the flexible substrate 6. On each plane formed on the flexible substrate 6, the magnetosensitive element 12 is arranged with the magnetosensitive surface facing outside.

  Further, as shown in FIG. 12A, the current path 11 is disposed inside the spiral flexible substrate 6. In this case, as shown in FIG. 12B, the magnetic sensitive elements 12a to 12h are arranged in a spiral shape with the central axis of the current path 11 as the central axis.

  According to the fourth usage pattern, the magnetic sensitive elements 12 a to 12 h are arranged in a spiral shape around the central axis of the current path 11. Thereby, the magnetosensitive elements 12a to 12h are arranged at equal intervals on the virtual circle C centering on the central axis of the current path 11 in plan view. Further, as described above, the directions of the main sensitivity axes 121a to 121h of the magnetosensitive elements 12a to 12h are parallel to the tangential direction of the virtual circle C on the main surface 31, and the directions of the sub sensitivity axes 122a to 122h are This is the radial direction of the virtual circle C on the main surface 31. For this reason, in the fourth usage pattern, by calculating the outputs of the magnetic sensitive elements 12a to 12h, the disturbance magnetic field appearing not only on the main sensitivity axis 121 but also on the secondary sensitivity axis 122 can be canceled, and the current path 11 The measurement accuracy of the current value can be improved.

  When the magnetosensitive elements 12a to 12d are elements whose resistance values change, such as magnetoresistive elements, a constant voltage is applied to the magnetosensitive elements connected in series, and the midpoint potential is used as a voltage signal to calculate the arithmetic circuit 13. Can be output.

  In addition, this invention is not limited to the said embodiment, It can change and implement variously. In the above-described embodiment, the size, shape, and the like illustrated in the accompanying drawings are not limited thereto, and can be appropriately changed within the scope of the effects of the present invention. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  The present invention can be used, for example, to detect the magnitude of a current for driving a motor of an electric vehicle or a hybrid car.

  This application is based on Japanese Patent Application No. 2011-219594 of an application on October 3, 2011. All this content is included here.

Claims (6)

A second sensitivity that is arranged at equal intervals on a virtual circle centered on the central axis in a plane orthogonal to the central axis of the current path through which the current to be measured flows, and is orthogonal to the first sensitivity axis and the first sensitivity axis A plurality of magnetosensitive elements each having an axis;
An arithmetic circuit that calculates a current value flowing through the current path based on outputs of the plurality of magnetosensitive elements,
The direction of the first sensitivity axis of the plurality of magnetosensitive elements is parallel to the tangential direction of the virtual circle, and the direction of the second sensitivity axis of the plurality of magnetosensitive elements is the radial direction of the virtual circle,
The current sensor, wherein the plurality of magnetosensitive elements are spirally arranged around a central axis of the current path . The direction of the first sensitivity axis of the plurality of magnetosensitive elements is a direction along the same circumferential direction of the virtual circle, and the direction of the second sensitivity axis of the plurality of magnetosensitive elements is the same of the virtual circle. A direction along the radial direction,
2. The current sensor according to claim 1, wherein the arithmetic circuit calculates the current value by summing outputs of the plurality of magnetosensitive elements. The sensitivities of the first sensitivity axes of the plurality of magnetosensitive elements are equal to each other,
The current sensor according to claim 2, wherein sensitivities of the second sensitivity axes of the plurality of magnetosensitive elements are equal to each other. Each of the magnetosensitive elements is a first group in which the direction of the first sensitivity axis is a direction along one circulation direction of the virtual circle, or the direction of the first sensitivity axis is the one rotation direction of the virtual circle. Belongs to one of the groups of the second group, which is the reverse direction of the circle,
The arithmetic circuit separately sums the outputs of the magnetosensitive elements belonging to the first group and the magnetosensitive elements belonging to the second group, and the total value in the first group and the total value in the second group 2. The current sensor according to claim 1, wherein the current value is calculated by performing differential processing on the current value. It said magnetically sensitive element is a GMR element, a current sensor according to any one of claims 1 to 4, wherein the second sensitivity axis is sub sensitivity axis. Current sensor according to any one of claims 1 to claim 5, wherein the second sensitivity axis is an axis that affects the sensitivity.

Images